In recent years, in electric vehicle, the wireless power transmission technology attracts lots of attention wherein the power is supplied from outside wirelessly without using a power supply cable. In the wireless power transmission technology, the method using a resonance phenomenon between two resonators is becoming the mainstream. The method in which the resonance frequencies between two resonators are approached, an alternating current and voltage near the resonance frequency is applied to the resonators and the resonance phenomenon between two resonators is used has a merit that it is capable of enlarging the distance between power transmission and reception comparing to the electromagnetic induction. In the wireless power transmission technology using the resonance phenomenon, a capacitor circuit is connected to the coil for power transmission and a resonance circuit is formed.
To the capacitor circuit of the charging devices requiring large power transmission such as electric vehicle, a large voltage and current is applied. In order to distribute the application of the large voltage and current and obtain a desired electrostatic capacity, a capacitor circuit is constituted by connecting a plurality of capacitor elements. For example, in Patent Document 1, a coil unit is disclosed wherein a capacitor circuit connected to the coil is constructed by a plurality of capacitor elements.